Commit 596d789a authored by Ming Lei's avatar Ming Lei Committed by Greg Kroah-Hartman

USB: set hub's default autosuspend delay as 0

This patch sets hub device's default autosuspend delay as 0 to
speedup bus suspend, see comments in code for details.
Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e6f30dea
......@@ -1614,6 +1614,41 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
desc = intf->cur_altsetting;
hdev = interface_to_usbdev(intf);
/*
* Set default autosuspend delay as 0 to speedup bus suspend,
* based on the below considerations:
*
* - Unlike other drivers, the hub driver does not rely on the
* autosuspend delay to provide enough time to handle a wakeup
* event, and the submitted status URB is just to check future
* change on hub downstream ports, so it is safe to do it.
*
* - The patch might cause one or more auto supend/resume for
* below very rare devices when they are plugged into hub
* first time:
*
* devices having trouble initializing, and disconnect
* themselves from the bus and then reconnect a second
* or so later
*
* devices just for downloading firmware, and disconnects
* themselves after completing it
*
* For these quite rare devices, their drivers may change the
* autosuspend delay of their parent hub in the probe() to one
* appropriate value to avoid the subtle problem if someone
* does care it.
*
* - The patch may cause one or more auto suspend/resume on
* hub during running 'lsusb', but it is probably too
* infrequent to worry about.
*
* - Change autosuspend delay of hub can avoid unnecessary auto
* suspend timer for hub, also may decrease power consumption
* of USB bus.
*/
pm_runtime_set_autosuspend_delay(&hdev->dev, 0);
/* Hubs have proper suspend/resume support. */
usb_enable_autosuspend(hdev);
......
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